Pneumocystis carinii is an opportunistic organism, widely prevalent but generally dormant until bodily defenses are compromised whereupon it attacks the host. Generally, it is present in the lungs, thus pneumonia, frequently fatal, is the consequence of an infective attack. Also, patient to patient transmission can occur between similarly immune-compromised patients. The loss of immunity is associated with defects in the cell mediated immunity as is the case with patients with hematologic immunosuppression deficiencies, patients with lymphoproliferative diseases, patients under cancer chemotherapy, and patients with AIDS or with immunosuppressed transplants. About one half of the AIDS patients develop P. carinii pneumonia and AIDS patients have accounted for most of the recent cases of this disease. Left untreated, the disease is 100 percent fatal.
The current method of treatment for P. carinii pneumonia is trimethoprim/sulfamethoxazole or pentamidine. Treatment with trimethoprim/sulfamethoxazole (TMP/SMZ) is associated with a high level of toxic side effects including rash, elevated liver function, nausea and vomiting, anemia, creatine elevation, and in extreme cases, Stevens Johnson syndrome. Side effects from TMP/SMZ are much more prevalent in patients with AIDS. Treatment with pentamidine is also associated with a high level of toxic side effects including renal failure, hepatotoxicity, hypoglycemia, hematologic abnormalities and pain or abscess at the injection site. The mortality attributable to treatment can reach 20 to 30 percent. An improved method for the treatment of P. carinii pneumonia in immune compromised patients is greatly needed.